Microbial Air Samplers are used in cleanrooms and aseptic environments to assess the level of bio-contamination within a pharmaceutical or medical device production space.
Microbial samplers are a form of active monitoring, and are available in both remote and portable versions; most operate via the principal of impaction, in which air, at a decided flow rate, is drawn through a plate with a numbers of holes at a specified diameter. As the air passes through the holes, its velocity is accelerated directed upon the surface of a solid medium, such as agar; particles that are above a certain cutoff diameter at the impaction velocity have too much inertial to make the 80 degree corner and are impacted onto the collection surface. After a decided volume of air/gas has passed over the collection surface, the sample is ended and the collection surface/agar is removed for incubation. After the incubation period, the collection surface is inspected and the number of visible colony forming units is counted. The number and or type of colony forming units present on the incubated agar gives a quantitative assessment of the sterility of the air that was present in the manufacturing space during the time of sampling.
Agar media, a jelly like substance used to capture particles and microorganisms above the cutoff size, is available in many formulations with varying mixes of agar (obtained from algae) and other nutrients. The gel's porous nature and semi-rigid structure help slow the microbes down without killing them (decelerating too fast) while providing a growth medium for the captured microorganisms to flourish. Typically in air sampling applications, the agar media is contained within a petri dish/plate for easy handling and sample integrity; the petri plate and agar media combination are commonly referred to as an agar plate. Agar plates are produced in a range of sizes ranging from 35 mm to 150 mm in diameter, though most typically the 100 mm size is used for air samplers.
In use, a new sterile agar plate is placed into the instrument prior to beginning a sample. The operator must carefully install the petri plate into the sampler's respective petri plate holder while only making contact with the external surfaces of the petri dish lid. The lid is then removed (leaving only the agar plate), the impactor cover/plate is installed, and the pump is started to begin the sample period. After the sample is completed (determined by the unit flow rate and the total desired sample volume), the impactor cover/plate is removed and the operator uses the lid that was previously removed to grip the agar plate; again, being sure to only touch the external surfaces of the lid so as to not entrain any foreign microbes into the agar media. The agar plate is then taken to a controlled environment for incubation, in which the microbial content is allowed to germinate. After a pre-determined incubation period, the agar plate is removed and inspected for Colony Forming Units. The number and type of colony forming units observed growing in the agar media can then be used to determine the relative sterility of the process at the time of the agar plate's sampler period.
Typically, the only part of the viable sampler that comes into contact with the agar plate is the mechanism that holds and supports the petri dish during the sample. In most applications that will make use of a viable sampler, the mechanism that holds the agar plate will require cleaning and sterilization prior to the installation of a new sterile agar plate. It is advantageous, in terms of time reduction and process control, to facilitate easy and fast cleaning/sterilization of the entire viable sampler; this is particularly true of the component/s that hold and support the agar plate during sampling.
Thus, there is a need for a new mechanism or component by which the entirety of the petri plate, including the agar plate, may be easily removed without the need for tools or unnecessary contact or contamination. Such a device preferably employs at least one magnet disposed within the top plate assembly and/or the top of an air sampler to facilitate the secure attachment and detachment of the top plate assembly to and from the air sampler. Indexing or gradations are preferably present to ensure proper alignment of the top plate assembly during attachment of the top plate assembly to the air sampler (after cleaning or reset).